When the House Ways and Means Committee heard testimony Tuesday from aggrieved organizations, all were conservative. Democrats were invited to have witnesses but declined.

“In the end, it doesn’t matter if it’s Democrat, Republican, conservative or liberal, it happens to all Americans,” explained Rep. Joseph Crowley of New York, the vice chairman of the House of Representatives Democratic Caucus.

The IRS’s targeting of conservative-leaning groups is the subject of investigations by the Treasury Department’s inspector general, the FBI and at least four congressional panels.

The controversy dogging the IRS is the most explosive for the agency since President Richard Nixon targeted his political enemies with a special unit created in the agency more than 40 years ago. After Nixon’s 1974 resignation in disgrace, the laws were changed to limit the ability of the executive and legislative branches to influence IRS audits and reviews. . . .